From patchwork Thu Aug 8 11:09:38 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Hogan X-Patchwork-Id: 265697 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 2EA072C00C9 for ; Thu, 8 Aug 2013 21:10:25 +1000 (EST) Received: from localhost ([::1]:45987 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V7O6o-0003NS-Dh for incoming@patchwork.ozlabs.org; Thu, 08 Aug 2013 07:10:22 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41567) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V7O6S-00033b-D0 for qemu-devel@nongnu.org; Thu, 08 Aug 2013 07:10:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V7O6K-0007Zb-Dw for qemu-devel@nongnu.org; Thu, 08 Aug 2013 07:10:00 -0400 Received: from multi.imgtec.com ([194.200.65.239]:13063) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V7O6K-0007Yz-7o for qemu-devel@nongnu.org; Thu, 08 Aug 2013 07:09:52 -0400 From: James Hogan To: qemu-devel Date: Thu, 8 Aug 2013 12:09:38 +0100 Message-ID: <1375960178-10882-1-git-send-email-james.hogan@imgtec.com> X-Mailer: git-send-email 1.8.1.2 MIME-Version: 1.0 X-Originating-IP: [192.168.154.65] X-SEF-Processed: 7_3_0_01192__2013_08_08_12_09_48 X-detected-operating-system: by eggs.gnu.org: Windows XP X-Received-From: 194.200.65.239 Cc: Anthony Liguori , James Hogan , Michael Roth Subject: [Qemu-devel] [PATCH] qemu-char: fix infinite recursion connecting to monitor pty X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Since commit bd5c51e (qemu-char: don't issue CHR_EVENT_OPEN in a BH), an infinite recursion occurs when putting the monitor on a pty (-monitor pty) and connecting a terminal to the slave port. This is because of the qemu_chr_be_event(s, CHR_EVENT_OPENED) added to qemu_chr_be_generic_open(). This event is captured by monitor_event() which prints a welcome message to the character device. The flush of that welcome message retriggers another open event in pty_chr_state() because it checks s->connected, but only sets it to 1 after calling qemu_chr_be_generic_open(). I've fixed this by setting s->connected = 1 before the call to qemu_chr_be_generic_open() instead of after, so that the recursive pty_chr_state() doesn't call it again. An example snippet of repeating backtrace: ... #107486 0x007aec58 in monitor_flush (mon=0xf418b0) at qemu/monitor.c:288 #107487 0x007aee7c in monitor_puts (mon=0xf418b0, str=0x1176d07 "") at qemu/monitor.c:322 #107488 0x007aef20 in monitor_vprintf (mon=0xf418b0, fmt=0x8d4820 "QEMU %s monitor - type 'help' for more information\n", ap=0x7f432be0) at qemu/monitor.c:339 #107489 0x007aefac in monitor_printf (mon=0xf418b0, fmt=0x8d4820 "QEMU %s monitor - type 'help' for more information\n") at qemu/monitor.c:347 #107490 0x007ba4bc in monitor_event (opaque=0xf418b0, event=2) at qemu/monitor.c:4699 #107491 0x00684c28 in qemu_chr_be_event (s=0xf37788, event=2) at qemu/qemu-char.c:108 #107492 0x00684c70 in qemu_chr_be_generic_open (s=0xf37788) at qemu/qemu-char.c:113 #107493 0x006880a4 in pty_chr_state (chr=0xf37788, connected=1) at qemu/qemu-char.c:1145 #107494 0x00687fa4 in pty_chr_update_read_handler (chr=0xf37788) at qemu/qemu-char.c:1121 #107495 0x00687c9c in pty_chr_write (chr=0xf37788, buf=0x70b3c008
, len=538720) at qemu/qemu-char.c:1063 #107496 0x00684cc4 in qemu_chr_fe_write (s=0xf37788, buf=0x70b3c008
, len=538720) at qemu/qemu-char.c:118 ... Signed-off-by: James Hogan Cc: Michael Roth Cc: Anthony Liguori Tested-by: Michael Roth --- Note the commit I mentioned Cc's gnu-stable@nongnu.org. Assuming this patch is acceptable it probably makes sense for it to follow the other patch into stable too. qemu-char.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/qemu-char.c b/qemu-char.c index 16f3ad7..1be1cf6 100644 --- a/qemu-char.c +++ b/qemu-char.c @@ -1142,8 +1142,8 @@ static void pty_chr_state(CharDriverState *chr, int connected) s->timer_tag = 0; } if (!s->connected) { - qemu_chr_be_generic_open(chr); s->connected = 1; + qemu_chr_be_generic_open(chr); s->fd_tag = io_add_watch_poll(s->fd, pty_chr_read_poll, pty_chr_read, chr); } }